Updated

A teenager who authorities say tried to recruit classmates for a mass shooting and bomb attack at his northeastern Oklahoma high school has been convicted in a plot to kill students, teachers and police officers.

A jury in Bartlesville found 19-year-old Sammie Eaglebear Chavez guilty of planning to cause bodily harm and recommended a 30-month prison term and $5,000 fine. The jury found him not guilty of conspiring to perform an act of violence.

Chavez had pleaded not guilty and testified in his own defense that he was joking when he told classmates about how a shooting and bomb attack could be carried out at Bartlesville High School.

"It was a joke in the sense that it wasn't meant seriously," Chavez told jurors, the Tulsa World newspaper reported. Bartlesville is 45 miles north of Tulsa.

Police and prosecutors said Chavez intended to lure students into the school's auditorium, chain the doors shut and shoot the students. Chavez also planned to place bombs by the auditorium doors and detonate them as police officers approached, according to an affidavit.

Chavez was arrested in December, hours before a gunman opened fire at a Connecticut elementary school and killed 20 children and six adults before killing himself.

Bartlesville police officer Jacob Moran testified that after arresting Chavez he found notes in the teen's pockets saying that "those who deserve to die will be killed," and that those who survive "will be forced to witness it," according to the Bartlesville Examiner-Enterprise.

Chavez testified that he had no intention to shoot or bomb the school, but admitted he was "angry at the world," and that writing the notes was a way for him "to release feelings of anger."

Prosecutors said Chavez tried to obtain a map of the school campus and had recently used a school computer to get information about a platform to support a .22-caliber rifle.

A student informed school officials about the plot -- police said Chavez tried to recruit classmates -- and the school officials called police. No one was injured.

Phone messages seeking comment from prosecutors and Chavez' defense attorney were not immediately returned late Tuesday afternoon.

Chavez' mother has said her son sent her a text message two days before his arrest saying that he wanted to "shoot up" the high school because he thought some students were talking about him behind his back. But she also said she didn't think her son would have carried out the attack.

"Deep down, I don't think my son would have done this," Jessie Chavez said shortly after her son was arrested. "That's not my son. My son laughs and makes jokes. He's always pulling pranks."

Chavez also said her son showed symptoms of possible mental illness and had been seeing a therapist, but the court found him competent to stand trial following a mental competency exam.